This application relates to the use of inserts having a variable opening formed within the insert to allow selection of the port size for an economizer or by-pass path in a compressor.
One type of sealed compressor that is becoming widely utilized in refrigerant compression applications is a scroll compressor. Scroll compressors present several design challenges. One particular design challenge is achieving a reduced cooling capacity level when full capacity operation of the compressor is not desired. In many situations, it may not be desirable to have full capacity of the compressor.
Thus, to achieve reduced capacity, scroll compressors have been provided with additional internal passages and an unloader by-pass valve which diverts a portion of the compressor refrigerant back to a compressor suction port. In this way, the mass of refrigerant being compressed is reduced. The size of the passages which communicate with the by-pass valve effects the amount of by-pass fluid and thus the amount by which the capacity is reduced.
On the other hand, in for other applications, there is a need to achieve increased capacity or to improve refrigerant cycle efficiency. One way of achieving increased capacity and improving efficiency is the inclusion of an economizer circuit in the refrigerant system. An economizer circuit essentially provides heat transfer between a main refrigerant flow downstream of the condenser, and a second refrigerant flow which is also tapped downstream of the condenser and an upstream of a main expansion valve. The main flow is cooled in a heat exchanger by the second flow. In this way, the main flow from the condenser is cooled before passing through its own expansion valve and entering the evaporator. Since the main flow enters the main expansion valve at a cooler temperature, it has greater capacity to absorb heat in the evaporator which results in increased system cooling capacity and improved cycle efficiency. The refrigerant from the second flow path enters the compression chambers of the compressor at an intermediate compression point downstream of suction. Typically, the second flow path economizer fluid is injected at a point after the compression chambers have been closed.
The use of economizer circuits has become more widespread in recent years.
It is also known in the prior art how the unloader and economizer function can be combined together. Such a system is shown in prior U.S. Pat. No. 5,996,364.
The economizer and unloader circuits are utilized to obtain optimum cooling capacity and improve cycle efficiency. Further control of capacity and efficiency improvement is achieved by varying the size of economizer and unloader passages. The optimum size of these passages is dependent upon compressor size, and the particular application. Thus, it would be desirable to have an easy way to vary the size of the economizer and unloader passages. To date, achieving variation in the size of the passages has required that the ports be machined into the elements of the compressor to a desired size. This results in machining difficulties, increased cycle time, the requirement of increased inventory, and challenges with regard to machining the exact optimum size economizer or unloader passages.
While it has been proposed to utilize inserts in scroll compressors to control the size of a discharge port, no such use has ever been proposed for economizer or unloader ports or passages.